1. Field of the Invention
The present invention relates to a specimen holder, and more specifically to an electron microscope specimen holder and a spacer used in the same. Even more specifically, the present invention relates to an electron microscope specimen holder useful in performing EDX (energy dispersive X-ray spectroscopy) analysis of a specimen produced by a focused ion beam (FIB) method, and a spacer used in the same.
2. Description of the Related Art
Transmission electron microscopes (TEM) are widely used not only in basic materials research, but also in the development of materials and devices as an indispensable analyzing means. In particular, in recent years, developments have been made in, for example, semiconductor-device film formation technology and micromachining. This has resulted in a demand for not only observations with higher resolution, but also analysis of very small areas. As a means for responding to these demands, transmission electron microscopes are becoming increasingly important. One method which is widely used in analyzing very small areas is the energy dispersive X-ray spectroscopy method.
In recent years, focused ion beam (FIB) processing devices have been developed, and are starting to be applied in various fields. They are typically used in the semiconductor-manufacturing field. A technology for producing a specimen of a specific portion of, for example, a semiconductor device to be sectionally observed using TEM is attracting attention as one technology to which focused ion beam processing devices can be applied. This technology is, in particular, used to produce a specimen (or to form thinner pieces) for TEM observation.
A description of a conventional side-entry-type specimen holder for an electron microscope will be given with reference to FIGS. 7 to 11 and FIG. 15. FIG. 15 is a schematic view of a conventional electron microscope device. In FIGS. 7 to 14, a longitudinal direction (or an X-axis direction) of a holder body 1 on which a specimen 21 is placed is substantially perpendicular to a direction (or a Z-axis direction) in which electrons are emitted from an electron-emitting means. FIG. 7 is a plan view schematically illustrating the specimen holder. FIG. 8 is an enlarged schematic view of portion A of FIG. 7, as viewed from the Z-axis direction. FIG. 9 is a sectional view along the X-axis direction (or the X-Z plane) of FIG. 8. FIG. 10 is a sectional view along the Y-axis direction (or the Y-Z plane) of FIG. 8. FIG. 11 is a sectional view showing a state in which the holder is tilted from its state in FIG. 10, with the X-axis as a center. In FIGS. 7 to 15, the X-axis directions, the Y-axis directions, and the Z-axis directions are consistently represented throughout.
The specimen holder shown in FIGS. 7 to 11 primarily comprises the holder body 1, a specimen-holding table 2 for holding the specimen 21, and a specimen holding-down means 3. The specimen 21 is held by being sandwiched between the specimen-holding table 2 and the specimen holding-down means 3. In this specimen holder, the specimen holding-down means 3 is secured to the specimen-holding table 2 with a screw 9 in order to hold the specimen 21. The holder body 1 includes protrusions which protrude beyond a specimen-holding surface 11 and a plane where a meshed section 23 is disposed (or beyond a plane where the specimen 21 is disposed). The protrusions are formed so as to protrude above the specimen-holding surface 11, the plane of the specimen-holding table 2, and the specimen 21 itself in the Z-axis direction in order to provide mechanical strength to the specimen holder itself. Here, the specimen-holding surface 11 of the specimen-holding table 2 and a specimen-holding surface 12 of the specimen holding-down means 3 are formed substantially parallel to a horizontal surface of the holder body 1. Here, the specimen-holding table 2 and the specimen holding-down means 3 do not comprise parts. Depending on the specimen-holding method, the specimen-holding table 2 and the specimen holding-down means 3 may comprise a plurality of component parts. The specimen holder is not provided with any other special functions. However, depending on the goniometer (not shown) installed in the electron microscope, the specimen 21 and the specimen holder body 1 are tilted (or rotated) with respect to the X-axis in FIG. 8 as a center, as shown in FIG. 11. Hereunder, the tilting direction shown in FIG. 11 is called a + direction, with the horizontal posture of the holder body 1 (shown in FIG. 10) serving as a reference.
Although not specifically illustrated, as disclosed in, for example, Japanese Patent Laid-open No. 11-185686, there are various types of specimen holders for electron microscopes. They include a biaxially tilting specimen holder, a specimen cooling holder, a specimen heating holder, a specimen pulling holder, and a combination thereof. The biaxially tilting specimen holder has a mechanism for tilting specimen-holding table 2, with a direction perpendicular to the longitudinal direction of the holder body 1 (or perpendicular to the X-axis direction in FIG. 8), that is, the Y-axis direction in FIG. 8, serving as a center axis for tilting. The specimen cooling holder has a mechanism for cooling specimen 21. The specimen heating holder has a mechanism for heating specimen 21. The specimen pulling holder has a mechanism for pulling specimen 21.
With reference to FIGS. 7 to 11, an example of the energy dispersive X-ray spectroscopy (EDX) analysis carried out using the conventional electron-microscope specimen holder will be described. In the EDX analysis, as shown in FIG. 15, when the specimen 21 held by the specimen holder is irradiated with electron beams, X-rays produced from the specimen 21 are detected by an X-ray analyzer 31 in order to obtain an energy spectrum. As shown in FIG. 10, when the angle of the center axis of the X-ray analyzer 31 from the specimen-holding surface 11 is small, the sensitivity with which X-rays are detected can be made large by decreasing the distance between the specimen 21 and the X-ray analyzer 31. Therefore, the X-ray analyzer 31 in which the angle of the center axis is small is becoming the dominating type of X-ray analyzer. In order to simplify the configuration, the X-ray analyzer 31 is mainly disposed in a direction perpendicular to the longitudinal direction (or in a direction perpendicular to the X-axis direction) of the specimen holder, that is, in the Y-axis direction of the specimen holder, as shown in FIG. 8.
Accordingly, it is an object of the present invention to provide an electron microscope holder having a high X-ray detection efficiency even in EDX analysis carried out on a specimen to be subjected to sectional TEM observation with an X-ray analyzer.
To this end, according to one aspect of the present invention, there is provided a specimen holder (a specimen-supporting member) comprising a specimen-holding table including a specimen-placing plane (or a specimen-holding surface); and a pair of protruding members (or protruding portions) protruding beyond the specimen-placing plane (or the specimen-holding surface) and having the specimen-holding table disposed therebetween. The specimen-holding surface (or the top surface) of the specimen-holding table (or the surface of the specimen-holding table where the specimen is placed) is formed at an angle from (that is, not parallel to) a plane including the top portions (or the top surfaces or the topmost portions) of the pair of protruding members (or protruding portions) protruding beyond the specimen-placing plane.
In the specimen holder of the present invention, the specimen-holding surface of the specimen-holding table (or the top surface of the specimen-holding table corresponding to the specimen-placing surface, or the meshed-section-placing surface, of the specimen-holding table may be formed at an angle of less than 45 degrees from the plane including the top portions (or the top surfaces or the topmost portions) of the pair of protruding members (or protruding portions) protruding beyond the specimen-placing plane. It is preferably formed at an angle of from 1 to 25 degrees inclusive.
According to another aspect of the present invention, there is provided a specimen holder (specimen-supporting means) comprising a specimen-holding table including a specimen-placing plane (or a specimen-holding surface); and a pair of protruding members (or protruding portions) protruding beyond the specimen-placing plane and having the specimen-holding table disposed therebetween. The specimen-holding surface (or the top surface) of the specimen-holding table (or the surface of the specimen-holding table where the specimen is placed) is formed at an angle from (that is, not parallel to) a line connecting top portions (or top surfaces or topmost portions) of the pair of protruding members (or protruding portions) protruding beyond the specimen-placing plane.
In the specimen holder of the present invention, the specimen-holding surface of the specimen-holding table (or the top surface of the specimen-holding table corresponding to the specimen-placing surface of the specimen-holding table) may be formed at an angle of less than 45 degrees from the line connecting the top portions of the pair of members protruding beyond the plane where a specimen is placed. It is preferably formed at an angle of from 1 to 25 degrees inclusive.
According to still another aspect of the present invention, there is provided a specimen holder for an electron microscope, comprising: a holder body, a specimen-holding table provided at the holder body and including a specimen-holding surface for placing a specimen thereon; and a specimen holding-down means for holding down the specimen on the specimen-holding table; wherein, when the holder body is in a horizontal posture, the specimen-holding surface of the specimen-holding table is tilted, with a longitudinal direction of the holder body defining a center axis of tilting.
The specimen holder for an electron microscope may further comprise an X-ray analyzer disposed so as to face a direction perpendicular to the longitudinal direction of the holder body, wherein the specimen-holding surface of the specimen-holding table may be tilted so that a side of the specimen-holding surface of the specimen-holding table closer to the X-ray analyzer becomes nearest to the X-ray analyzer.
The specimen holding-down means may include a specimen-holding surface which is correspondingly tilted with the tilted specimen-holding surface of the specimen-holding table.
The specimen holder may further comprise a mechanism for tilting the specimen-holding table, with a direction perpendicular to the longitudinal direction of the holder body defining a center axis of tilting.
The specimen-holding table may integrally be formed with the holder body.
The specimen-holding table may comprise a specimen-holding-table base section formed integrally with the holder body, and a specimen-holding-table spacer having the specimen-holding surface and being removable from the specimen-holding-table base section.
The specimen holding-down means may comprise a specimen-holding-down-means base section and a specimen-holding-down-means spacer having a specimen-holding surface and being removable from the specimen-holding-down-means base section.
According to still another aspect of the present invention, there is provided a specimen-holder spacer for an electron microscope used in a specimen holder comprising a holder body, a specimen-holding table provided at the holder body and used to place a specimen thereon, and a specimen holding-down means for holding down the specimen on the specimen-holding table;
wherein the spacer includes a specimen-holding surface for placing the specimen thereon, and is removable from the specimen-holding table; and
wherein when the holder body is in a horizontal posture, the specimen-holding surface of the spacer mounted to the specimen-holding table is tilted, with a vicinity of a longitudinal direction of the holder body defining a center axis of tilting.
In the specimen-holding spacer embodiment, as in the embodiments without spacers, in the spacer, an X-ray analyzer may be disposed so as to face a direction perpendicular to the longitudinal direction of the holder body. In addition, the specimen-holding surface of the spacer may be tilted so that a side of the specimen-holding surface of the spacer mounted to the specimen-holding table nearest to the X-ray analyzer becomes closer to the X-ray analyzer.
The specimen holding-down means may include a specimen-holding surface correspondingly tilted with the specimen-holding surface of the spacer mounted to the specimen-holding table.
According to still another aspect of the present invention, there is provided a specimen-holder spacer used in an electron microscope specimen holder comprising a holder body, a specimen-holding table provided at the holder body and used to place a specimen thereon, and a specimen holding-down means for holding down the specimen on the specimen-holding table;
wherein when the specimen holding-down means having the spacer mounted thereto is further mounted to the specimen-holding table and when the holder body is in a horizontal posture, the specimen-holding surface of the spacer is tilted, with a longitudinal direction of the holder body defining a center axis of tilting.
In the specimen holder, an X-ray analyzer may be disposed so as to face a direction perpendicular to the longitudinal direction of the holder body. In addition, the specimen-holding surface of the spacer may be tilted so that a side of the specimen-holding surface of the spacer mounted to the specimen-holding table and the specimen holding-down means closer to the X-ray analyzer becomes nearest to the X-ray analyzer.
The specimen-holding table may include a specimen-holding surface which is correspondingly tilted with the specimen-holding surface of the spacer mounted to the specimen holding-down means.
According to still another aspect of the present invention, there may be provided a specimen holder (specimen-supporting means) for an electron microscope comprising:
a holder body;
a specimen-holding table provided at the holder body, the specimen-holding table having a specimen-holding surface for placing a specimen thereon; and
a specimen holding-down means for holding down the specimen on the specimen-holding table;
wherein the specimen-holding table is provided at the holder body through a tilting mechanism; and
wherein the tilting mechanism tilts (rotates) the specimen-holding table, with a longitudinal direction of the holder body defining a center axis of tilting (rotating).
The specimen holder may further comprise an X-ray analyzer disposed so as to face the direction perpendicular to the longitudinal direction of the holder body.
The specimen holder may further comprise a mechanism for tilting the specimen-holding table, with a direction perpendicular to the longitudinal direction of the holder body defining the center axis of tilting.
In each specimen-holding member (specimen-supporting means) having the above-described corresponding structure in accordance with the present invention, each specimen-holding surface is tilted (rotated), with the longitudinal direction (or the X-axis direction) of its corresponding holder body defining the tilting (rotating) axis. In addition, each specimen-holding surface is tilted so that the side of each specimen-holding surface nearest to its corresponding X-ray analyzer becomes closer thereto. Accordingly, even when the optimal tilting angle for observing the specimen itself is small, the tilting angle of each specimen holder itself can be made large. Consequently, it is possible to mitigate the problem of X-rays produced from the specimen being subjected to EDX analysis being intercepted by an edge (a protrusion) of a specimen holder. Because of this, it is possible to mitigate the problems of X-ray detection efficiency being reduced or of X-rays not being detected. These operational features are particularly beneficial when carrying out EDX analysis of specimen, such as a specimen to be subjected to sectional TEM observation produced by the FIB method, whose optimal tilting angle is small, with the X-axis direction of the specimen itself defining the tilting axis during TEM observation.
Each specimen holder having the above-described structure in accordance with the present invention may comprise a mechanism for tilting (rotating) the specimen-holding table, with the longitudinal direction (or the X-axis direction) of the holder body defining the center axis of tilting (rotating). Therefore, the tilting (rotating) angle when the X-axis direction of the specimen-holding surface or the specimen itself defines the tilting axis can be made to differ from the tilting angle when the X-axis direction of the specimen holder itself defines the tilting axis (the tilting angle being formed using a tilting mechanism, such as a goniometer of an electron microscope). In other words, by tilting the specimen-supporting table in one direction using the tilting mechanism of the specimen holder, and, at the same time, by tilting the specimen holder itself in the opposite direction using, for example, a goniometer, the tilting angle of the specimen holder can be made large even when the optimal tilting angle for observing the specimen itself is small. With this arrangement, it is possible to mitigate the problem of the X-rays produced from the specimen during EDX analysis being intercepted by an edge of the specimen holder. Therefore, it is possible to mitigate the problems of the detection efficiency of the X-rays produced from the specimen being reduced and not being detected. This operational feature is particularly beneficial when carrying out EDX analysis of a specimen, such as a specimen to be subjected to TEM observation produced by the FIB method, whose optimal tilting angle is small, with the X-axis direction of the specimen itself defining the tilting axis during TEM observation.